Urethane-modified polyisocyanurate foam

ABSTRACT

A urethane-modified polyisocyanurate foam obtained by reacting (A) a polyisocyanate compound component, (B) a polyol component, containing a modified phenolic resin obtained by adding 20 to 100 parts by weight of a polyhydric alcohol or its alkylene oxide adduct to 100 parts by weight of a benzylic ether type phenolic resin and heating under a reduced pressure, in an amount of at least 3 wt % to the total resin component, (C) water and (D) a foam stabilizer comprising a mixture of at least 2 silicone type surfactants having different surface tensions wherein a surfactant having a higher surface tension has a surface tension of higher than 22 dyne/cm and a surfactant having a lower surface tension has a surface tension of at most 22 dyne/cm, in the presence of (E) a urethane-forming catalyst and/or a trimerization catalyst.

[0001] The present invention relates to a urethane-modifiedpolyisocyanurate foam having a high expansion rate, which is excellentin flame retardancy and heat resistance, and is low in smoke generation,without using chlorofluorocarbons (CFCs) or hydrochlorofluorocarbons(HCFCs) as a blowing agent.

[0002] In the polyurethane and polyisocyanurate industries, because of aproblem of depleting the ozone layer, use of CFCs, which had been usedas versatile and effective blowing agents, has been banned since 1995,and further, even HCFCs, substitutes for CFCs, having much lower ozonedepletion potential, are scheduled to be banned from the year of 2003.Hence, a variety of alternative blowing agents, such ashydrofluorocarbons (HFC), hydrocarbons (HC), carbon dioxide (CO₂), etc.are being studied.

[0003] It is said lately that HCFC blowing is being replaced by the CO₂blowing for the polyurethane foam (PUR system) for insulated metalsidings or panels, and that the replacement has been almost completed.

[0004] However, in the case of the polyisocyanurate foam (PIR system),which is rated high for the flame retardancy and heat resistance, whenthe CO₂ blowing method is applied, there are specific problems of lowerthan typical flame retardancy, heat resistance and shrinkage(deformation) with time, in addition to a problem of unsatisfactoryadhesion to a facing material, not allowing the replacement of theconventional blowing method by the CO₂ blowing to develop assuccessfully as in the case of PUR systems.

[0005] In the CO₂ blowing method, it is generally said that a foamcauses shrinkage (deformation) with time. This is because of the rapiddiffusion of CO₂ from the foam cells.

[0006] In the field of insulated metal sidings or panels cored with thePUR system, the replacement by the CO₂ blowing method has been almostcompleted by lowering a closed cell ratio as a means for preventingshrinkage (deformation) with time. For example, by employing acombination of a high molecular polyol and a low molecular polyol, theresulting foam becomes rich with open cells and, because of its lowdensity, does not cause shrinkage.

[0007] In the field of insulated metal sidings or panels cored with thePIR system, a foam having an open cell structure can be obtained toprevent shrinkage (deformation) by employing a method of using certainaromatic polyester polyols (JP-A-10-231345), and a method of producing afoam of relatively low density by using a trimerization catalyst and acarbodiimide-forming catalyst in combination (Japanese Patent No.2,972,523), but there are problems of lowering flame retardancy, heatresistance and a poor adhesion to a facing material, and it is thereforedifficult to use the CO₂ blowing as a substitute for the conventionalblowing methods.

[0008] In order to solve the above-mentioned problems of a PIR type foamemploying a CO₂ blowing agent, it is necessary not only to make a foamhaving a continuous cell phase (open cells) for improving the shrinkageproblem but also to solve the above-mentioned problems concerning flameretardancy and heat resistance.

[0009] In order to solve the above-mentioned problems, the presentinventors have discovered a novel method not only for freely controllinga cell size but also for improving flame retardancy and heat resistanceby applying a benzylic ether type phenolic resin (hereinafter referredto as “BEP”) to the PIR system.

[0010] Particularly, flame retardancy and heat resistance are improvedby employing BEP as a polyol component and a cell size is controlled bymixing surfactants, having different properties, at an appropriateratio. For example, a silicone type surfactant is used as a foamstabilizer (1) and a dimethylsilicone oil is used as a foam stabilizer(2).

[0011] More particularly, the present invention provides aurethane-modified polyisocyanurate foam obtained by reacting (A) apolyisocyanate compound component, (B) a polyol component (said polyolcomponent contains a modified phenolic resin (hereinafter referred to as“modified BEP”) obtained by adding 20 to 100 parts by weight of apolyhydric alcohol or its alkylene oxide adduct to 100 parts by weightof a benzylic ether type phenolic resin and heating under a reducedpressure, in an amount of at least 3 wt % to the total resin component),(C) water and (D) a foam stabilizer comprising a mixture of at least 2silicone type surfactants having different surface tensions wherein asurfactant having a higher surface tension has a surface tension ofhigher than 22 dyne/cm and a surfactant having a lower surface tensionhas a surface tension of at most 22 dyne/cm, in the presence of (E) aurethane-forming catalyst and/or a trimerization catalyst.

[0012] The polyol component (B) used in the present invention is amixture of modified BEP and a polyol generally used for producing aurethane foam. Thus, the polyol component (B) comprises mainly modifiedBEP obtained by adding 20 to 100 parts by weight of a polyhydric alcoholor its alkylene oxide adduct to 100 parts by weight of a benzylic ethertype phenolic resin and heating the mixture under a reduced pressure, asdescribed in JP-B-7-30155. Examples of other polyols usable with themodified BEP include difunctional polyols such as ethylene glycol,diethylene glycol, polyethylene glycol, propylene glycol, dipropyleneglycol, polypropylene glycol, polytetramethylene glycol, 1,4-butanediolor these difunctional polyols addition-polymerized with one or two ormore kinds of alkylene oxides, trifunctional polyols such astrimethylolpropane, glycerin or these trifunctional polyolsaddition-polymerized with alkylene oxides, polyfunctional polyols suchas pentaerythritol, sorbitol, sugar or these polyfunctional polyolsaddition-polymerized with alkylene oxides, alkanolamineaddition-polymerized with an alkylene oxide, an aromatic polyesterpolyol, an acryl polyol resin, and the like, and these polyols may beused alone or may be used in a mixture of two or more polyols. Themodified BEP is used suitably in an amount of at least 3.0 wt to thetotal resin component. If the amount of the modified PET is less than3.0 wt %, flame retardancy, heat resistance and low smoking propertybecome poor.

[0013] A polyisocyanate compound (A) used in the present invention isnot specially limited and may be ones generally used in the preparationof a polyurethane foam, examples of which include m- or p-phenylenediisocyanate, p-xylene diisocyanate, ethylene diisocyanate,tetramethylene 1,4-diisocyanate, hexamethylene-1,6-diisocyanate,diphenylmethane-4,4′-diisocyanate,3,3′-dimethyldiphenylmethane-4,4′-diisocyanate,3,3-dichloro-4,4′-biphenylene diisocyanate or 1,5-naphthalenediisocyanate, 2,4- and 2,6-tolylene diisocyanate and their mixture,crude tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, crudediphenylmethane diisocyanate, and the like. These isocyanate compoundsmay be used alone or in a mixture of two or more. Its amount used is anequivalent ratio of an isocyanate group/active hydrogen in a polyolcomponent mixture solution in a range of from 1.05 to 5.0, preferablyfrom 1.50 to 3.0. If the above equivalent ratio is less than 1.05, flameretardancy, heat resistance and low smoking property become poor, and ifthe equivalent ratio is more than 5.0, a foam produced becomes brittleand adhesiveness to a facing material becomes poor.

[0014] A foam stabilizer used in the present invention is a mixture ofat least two kinds of silicone type surfactants having different surfacetensions, and a component having a higher surface tension has a surfacetension higher than 22 dyne/cm. A foam stabilizer generally used in thepreparation of a urethane foam may be used, preferable example of whichinclude an organic polysiloxane copolymer, apolydimethylsiloxane·polyalkylene oxide adduct, avinylsilane·polyoxyalkylene polyol compound and the like. A componenthaving a lower surface tension has a surface tension lower than 22dyne/cm, preferable examples of which include a dimethylsilicone oil.

[0015] Examples of the organic polysiloxane copolymer include SH-190,SH-192, SH-193, SH-194, M505, M507, M509 and SRX253 manufactured byToray Silicone K.K., L-520, L-540, L-580, L-582, L-5340, L-5410, L-5420,L-5470 and SZ-1127 manufactured by UNICAR CO., LTD., TFA-4200, TFA-4205and TFA-7241 manufactured by Toshiba Silicone K.K., and B-8404 andB-8017 manufactured by GOLDSCHMIDT K.K.

[0016] Examples of the dimethylsilicone oil include SH-200 manufacturedby Toray Silicone K.K., and TSF-451-5, TSF451-50 and TSF405 manufacturedby Toshiba Silicone K.K.

[0017] A suitable mixing ratio of a component having a higher surfacetension/a component having a lower surface tension is 100 parts byweight/0.5-50 parts by weight. If the amount of the component having alower surface tension is less than 0.5 part by weight, the aimed effectof the present invention can not be achieved, and shrinkage is caused.On the other hand, if the amount of the component having a lower surfacetension is more than 50 parts by weight, a foam-breaking effect becomeslarge and a satisfactory foam can not be obtained. A foam stabilizer (D)comprising a mixture of at least two kinds of silicone type surfactantshaving different surface tensions is used preferably in an amount offrom 0.5 to 10 parts by weight to 100 parts by weight of a polyolcomponent (B).

[0018] A catalyst used for carrying out urethane-foaming reaction may beones generally known as a urethane-foaming catalyst, examples of whichinclude N,N,N′,N′-tetramethylethylenediamine,N,N,N′,N′-tetramethylpropane-1,3-diamine,N,N,N′,N′-tetramethylhexene-1,6-diamine,N,N,N′,N″,N″-pentamethyldiethylenetriamine, N,N-dicylcohexylmethylamine,bis(N,N-dimethylaminoethylpiperazyl)ethane,N,N′,N″-tris(diethylaminopropyl)hexahydrotriazine and other tertiaryamine, and dibutyltin dilaurate, dibutyltin diacetate, and the like.These catalysts may be used alone or in a mixture thereof.

[0019] An isocyanate trimerization catalyst used in the presentinvention may be a trimerization catalyst for isocyanates used in thepreparation of a conventional polyisocyanurate resin. Examples of theisocyanate trimerization catalyst include an organic metal salt systemsuch as potassium acetate, potassium octenate, iron oxalate or the like,a tertiary amine salt such as 2,4,6-tris(dimethylaminomethyl)phenol,N,N′,N″-tris(dimethylaminopropyl)hexahydrotriazine or the like.

[0020] An urethane-foaming catalyst and a trimerization catalyst (E) areused in an amount of from 0.3 to 15 parts by weight, preferably from0.70 to 10 parts by weight to 100 parts by weight of a polyol component(B).

[0021] Water (C) used in the present invention reacts with apolyisocyanate compound to produce carbon dioxide and works as a foamingagent. An amount of water is determined depending on an aimed density ofa foam, and is suitably from 2 to 30 parts by weight to 100 parts byweight of a polyol component (B). If the amount of water is less than 2parts by weight, a density of a foam becomes too high, and if the amountof water exceeds 30 parts by weight, a mechanical strength becomes toolow for practical use.

[0022] In the present invention, if necessary, a crosslinking agent anda viscosity-reducing agent may be used. Examples of the crosslinkingagent include ethylene glycol, propylene glycol, 1,4-butanediol,1,6-hexanediol, diethylene glycol, triethylene glycol, triethanolamine,ethylenediamine or the like, and they may be used alone or in acombination of two or more. Examples of the viscosity-reducing agentinclude nitrogen-containing type, sulfur-containing type, phosphorustype, ether type, hydrocarbon type, ester type or carbonate type organiccompounds which are liquid at normal temperature, and they may be usedalone or in a combination of two or more. These additives and otheradditives may be previously mixed with a mixture containing a polyolcomponent (B) or may be added thereto at the time of reacting.

[0023] In the production of a polyisocyanurate foam of the presentinvention, a high pressure foaming machine, a medium pressure foamingmachine or a low pressure foaming machine is used to produce a board, apanel or a siding in a factory or to carry out in-situ foaming.

EXAMPLES

[0024] Hereinafter, the present invention is concretely illustrated withreference to Examples and Comparative Examples.

[0025] Starting materials employed, measurement methods and preparationmethods of samples in the Examples and Comparative Examples areillustrated below, and “%” is based on weight.

[0026] A density was measured in accordance with JISA-9511.

[0027] A closed cell foam ratio was measured in accordance withASTM-DT2856.

[0028] A flame retardancy test was carried out by employing a surfacetest with a Flammability Tester of Toyo Seiki Seisakusho, in accordancewith JIS A-1321.

[0029] In the following Examples and Comparative Examples, suchcompositions as shown in the following Table 1 were mixed and stirred at4,000 rpm in a laboratory mixer, and a foam was produced by using analuminum-made box.

[0030] A foam was obtained by subjecting the mixture to free-foaming inan aluminum-made box of 250 mm×250 mm×250 mm heated at 40° C. A corepart of the free-foamed foam was taken by cutting and was subjected to atest.

[0031] Starting materials employed were as follows.

[0032] Modified BEP: Modified phenolic resin (BEP2100M manufactured byHodogaya Chemical Co., Ltd.)

[0033] Other polyol 1: Aromatic polyester polyol (PL-135, OH value 200,manufatured by Toho Rika K.K.)

[0034] Other polyol 2: Glycerine polyether polyol (MF-78, OH value 35,manufatured by Takeda Chemical Industries, Ltd.)

[0035] TEP: Triethyl phosphate (flame retardant manufactured by BayerLtd.)

[0036] Trimerization catalyst: Potassium octenate (manufactured byPELRON Co.)

[0037] Foam stabilizer (1): Organic polysiloxane copolymer (SH-190,surface tension 23.5 dyne/cm, manufactured by Toray Silicone K.K.)

[0038] Foam stabilizer (2): Dimethylsilicone oil (TSF-451-100, surfacetension 20.8 dyne/cm, manufactured by Toshiba Silicone K.K.)

[0039] Isocyanate compound: Crude diphenylmethane diisocyanate (MR-100,NCO content 31.0%, manufactured by Nippon Polyurethane Industry Co.,Ltd.)

EXAMPLE 1

[0040] Predetermined compositions as shown in the following Table 1 wereprepared, and foams were produced in accordance with the predeterminedmethod, and densities and closed cell foam ratios were measured.Compositions A-1 to A-3 were different only in respect of a blendingratio of the foam stabilizers (2), and respective weight ratios of thefoam stabilizer (2) to the total amount were 0.03%, 0.06% and 0.12%.

[0041] Compositions and physical properties are shown in the followingTable 1.

[0042] As evident from the test results as shown in the following Table1, it was proved that a high extent of foaming could be achieved, and aclosed cell foam ratio could be controlled by varying a kind and ablending ratio of foam stabilizers, whereby an excellent dimensionalstability could be obtained. TABLE 1 (Compositions and physical propertymeasuring results) Examples (Compositions of present ComparativeExamples invention) Conventional Components Starting materials used A-1A-2 A-3 A-4 product B-1 B-2 B Modified BEP 15.8 15.8 15.8 15.0 — 15.815.8 Other polyol 1 31.6 31.6 31.6 30.1 57.6 31.6 31.6 Other polyol 231.6 31.6 31.6 30.1 14.3 31.6 31.6 TEP 11.8 11.8 11.8 11.2 18.0 11.811.8 E Trimerization catalyst 3.1 3.1 3.1 3.0 2.9 3.1 3.1 D Foamstabilizer (1) 1.1 1.1 1.1 1.0 2.9 1.2 — Foam stabilizer (2) 0.1 0.2 0.40.2 — — 1.2 C Water 4.8 4.8 4.8 9.5 4.9 4.8 4.8 A Isocyanate 221.0 221.0221.0 406.0 183.0 221.0 221.0 NCO/OH equivalent ratio 1.9 1.9 1.9 1.91.9 1.9 1.9 Foam density (kg/m³) 26.5 27.1 27.8 18.3 35.0 23.6 — Closedcell foam ratio (%) 50 15 0 15 98 98 — Dimensional  80° C. × 48 H −0.3−0.1 −0.2 −0.5 −15 Large Foam stability −20° C. × 48 H 0.5 0 0 1.2 −11shrinkage was not (ΔV)  70° C. × 95% −1.5 −0.8 −0.5 −0.9 −18 at roomformed.  RH × 48 H temp.

EXAMPLE 2

[0043] A test sample of 200 mm×100 mm×25 mm panel was prepared by usingcomposition A-2 of Example 1 and a colored galvanized steel sheetshaving a thickness of 0.35 mm as facing materials on both sides, and thetest sample thus prepared was subjected to a time variability test undersevere conditions as shown in Table 2, and the results are shown inTable 2.

[0044] As evident from the test results as shown in the following Table2, it was proved that the test sample was satisfactorily stable(excellent in thickness change rate) both at a high temperature and at alow temperature, and was satisfactory for practical use. TABLE 2 (Timevariability test) Composition A-2 of Thickness change rate (%) Example 1of present Days lapsed invention 5 days 10 days 20 days 30 days  80° C.−0.2 −0.3 −0.3 −0.3 −20° C. 0.1 0.2 0.2 0.2

EXAMPLE 3

[0045] In order to prove a heat resistance effect of the presentinvention, a heat resistance test was carried out to measure a volumechange rate, and the results are shown in the following Table 3.

[0046] A test sample was prepared by using composition A-2 of Example 1in accordance with a predetermined method.

[0047] As evident from the test results as shown in the following Table3, the heat resistance effect achieved by adding modified BEP becameremarkable under high temperature conditions. TABLE 3 (Heat resistancetest) Volume change rate (%) Test conditions 90° C. × 150° C. × 200° C.× 250° C. × Sample foams 48 H 48 H 2 H 2 H Composition A-2 −0.6 −3.3−1.5 −7.5 of Example 1 of present invention General-purpose −1.0 −3.9−3.3 −13.2 PIR (Comparative Example to Example 1)

EXAMPLE 4

[0048] A flame retardancy test was carried out, and the test results areshown in the following Table 4.

[0049] A test sample of 220 mm×220 mm×25 mm was prepared from a foamobtained by using composition A-2 of Example 1 in accordance with apredetermined method.

[0050] As evident from the test results as shown in the following Table4, it was proved that the aimed effect of the present invention could beachieved also in respect of flame retardancy. TABLE 4 (Flame retardancytest) After- Acceptance flame or CA T · d  (sec) rejection CompositionA-2 41  75  0 Acceptance of Example 1 of present invention JISA-1321Flame At most At most At most retardant rating 60 100 30 2

EXAMPLE 5

[0051] A product of the present invention and a conventional typicalproduct blown by an HCFC were compared in respect of board physicalproperties, a flame retardancy test and an asphalt test, and the resultsare shown in the following Table 5. A test sample of a board of thepresent invention was prepared by using composition A-1 of Example 1.

[0052] As evident from the test results as shown in the following Table5, the test sample obtained by using a CO₂ foaming agent in accordancewith the present invention was proved to be in no way inferior to theconventional product obtained by the using flon foaming agent, and wassatisfactory for practical use, and was proved to provide excellentperformances as a heat-insulating board for a water-proofing system.TABLE 5 (Physical properties of board) Flame retardancy test was carriedout in accordance with JIS A-9511. Dimensional stability was expressedby change rates. Composition A-1 of Example 1 Products of HCFC-blownpresent conventional invention products Board thickness (mm) 25 50 25 50Density (kg/m³): Entire core 52.2 40.8 57.1 42.1 A central part of core41.3 30.1 40.0 27.3 Compression strength (kg/cm²) 1.9 1.6 2.3 1.6 Closedcell foam ratio % 55 45 80 75 Dimensional Wet heat property stability(70° C., 95%, 48 H) Length −0.1 0 3.2 2.5 Breadth 0 −0.4 3.3 2.2Thickness 1.4 1.2 0.4 0.1 Heat resistance (80° C., 48 H) Length −0.1 0.21.2 0.5 Breadth 0.2 0 1.0 0.2 Thickness 0.5 0.2 −0.4 −0.5Low-temperature resistance (−20° C., 48 H) Length 0 0.2 −0.1 −0.1Breadth 0 0 0.1 0 Thickness 0.1 0.1 0.1 0.1 Water absorption (g/100 cm²)0.6 0.4 0.7 1.4 Flame Flame-out time (sec)  0-24  2-28  0-56  2-52retard- Burned distance (mm) 10-30 13-28 23-52 18-48 ancy Acceptance orA A A A Rejection Asphalt test (250° C., 5 sec) Length 0 0 0 0 Breadth 00 0 0

EXAMPLE 6

[0053] The aimed effect of the present invention was studied with regardto a dimensional stability test and a flammability test. The testresults are shown in the following Table 6.

[0054] A test sample of a siding having a structure comprising analuminum foil 20 μ, a PIR foam 9 mm and a colored aluminum plate 0.35 mmwas prepared in a continuous line.

[0055] As evident from the test results as shown in the following Table6, it was proved that the aimed effect of the present invention wasachieved also in respect of the test of siding. Also, it was proved thatthe product of the present invention meets the Class 2 non-flammabilityrequirements in JIS A-1321, thereby fully proving itself to bepractically usable. TABLE 6 (Physical property measuring results ofsiding) 1) Dimensional stability test   Thickness change ratio % Testconditions 80° C., 48 H 70° C., 95% RH, 48 H −20° C., 48 H CompositionA-3 −0.4 0.3 0.1 of Example 1 2) Flammability test JIS A-1321 Boringtest Flame retardancy rating 2 After- Acceptance flame or CA T · d (sec) rejection Composition A-3 33 20 9 Acceptance of Example 1

[0056] As mentioned above, the present invention provides a satisfactoryurethane-modified polyisocyanurate foam (PIR system) without using a CFCfoaming agent or HCFC, which has a low shrinkage, a low density andsatisfactory properties in respect of flame retardancy, heat resistance,adhesiveness and reactivity.

[0057] The entire disclosure of Japanese Patent Application No.2000-361130 filed on Nov. 28, 2000 including specification, claims andsummary are incorporated herein by reference in its entirety.

What is claimed is:
 1. A urethane-modified polyisocyanurate foamobtained by reacting (A) a polyisocyanate compound component, (B) apolyol component, containing a modified phenolic resin obtained byadding 20 to 100 parts by weight of a polyhydric alcohol or its alkyleneoxide adduct to 100 parts by weight of a benzylic ether type phenolicresin and heating under a reduced pressure, in an amount of at least 3wt % to the total resin component, (C) water and (D) a foam stabilizercomprising a mixture of at least 2 silicone type surfactants havingdifferent surface tensions wherein a surfactant having a higher surfacetension has a surface tension of higher than 22 dyne/cm and a surfactanthaving a lower surface tension has a surface tension of at most 22dyne/cm, in the presence of (E) a urethane-forming catalyst and/or atrimerization catalyst.
 2. The urethane-modified polyisocyanurate foamdescribed in claim 1, having a density of from 15 kg/m³ to 50 kg/m³. 3.The urethane-modified polyisocyanurate foam described in claim 1, foruse as a heat-insulating board for a water-proof roofing system.
 4. Theurethane-modified polyisocyanurate foam described in claim 2, for use asa heat-insulating board for a water-proof roofing system.
 5. Theurethane-modified polyisocyanurate foam described in claim 1, comprisinga core material for a panel.
 6. The urethane-modified polyisocyanuratefoam described in claim 2, comprising a core material for a panel. 7.The urethane-modified polyisocyanurate foam described in claim 1,comprising a core material for a metal siding.
 8. The urethane-modifiedpolyisocyanurate foam described in claim 2, comprising a core materialfor a metal siding.